An electronics current transformer is designed in which measured data and optical power are transmitted via optical fibers between the high-voltage level and the ground potential. A 1-km-long link is considered between a control unit and a measuring unit which experiences -30 to +70oC temperature changes. The system is able to deliver about 10 mW of electrical power required by the sensing unit for coding and transmitting through time division multiplexing: high-voltage current data in the form of a 1 Mb/s PCM optical signal, sensor head temperature, and supply voltage both in the form of PPM signals at a frame rate of 10 kHz. Optical to electrical conversion efficiencies are included between 30 and 40% according the temperature. So the supply voltage information is used in a servo control loop in order to minimize the output power level of the high-power laser diode and to improve the system reliability. The transmission rate and the multiplexing of data channels show an optical channel capacity well enough utilized in contrast with usual investigations in power-by-light technology where modest amounts of information are transmitted.